The concept of reversible mailing envelopes that can be closed and mailed to the receiver, after which the receiver can then open the envelope and use the same envelope for a return mailing, is quite old, patents having been granted on this concept in the United States at least as early as 1899 (U.S. Pat. No. 636,415). Prior to the development of releasable and reusable glues, envelope closures were generally effected by tongue-and-eye closures of the type now commonly found on larger so-called clasp envelopes (such as a 9".times.12"number 9 envelope).
With the development of releasable adhesives, simplified reversible envelopes were developed, such as the reversible envelope described in U.S. Pat. No. 4,210,250 to Robert S. Yale which used a combination of releasable and permanent adhesives in the preparation of an envelope that could be opened to a flat envelope blank and refolded in the opposite direction to produce an envelope in which the original interior of the envelope now formed the exterior of the re-folded envelope.
Additional improvements continued to be made, generally relating to the portion of the envelope referred to as the flap. One of the problems that has arisen with reversible envelopes that resemble standard letter envelopes is the tendency of the user to open them in a manner that destroys the reusable nature of the envelope, such as by tearing off an end of the envelope or by opening the top with a letter opener. To avoid this problem, recent envelope flaps have been developed that can be opened by a pull tab or similar feature which is readily apparent to the user, thereby ensuring that the envelope is opened in a manner which allows its reuse. For example, U.S. Pat. No. 4,917,287 to William W. Watson describes a reversible envelope in which the flap comprises a pull-tab portion which both opens the flap of the envelope and makes accessible an adhesive area that can be used to reseal the envelope when the envelope is refolded for returning to the sender. Unfortunately, the envelope flap in this patent is prepared from two body members that must be attached to each other by an adhesive, which increases the expense and difficulty of manufacture.
Additionally, designs that provide for easy opening of the return envelope are very useful, since bulk opening of return envelopes is a time consuming process.
New designs that simplify construction while still retaining the desirable characteristics of providing the recipient of the envelope with an opening technique that discourages non-reusable opening maneuvers and providing an easy-opening return envelope, are therefore desirable.